Renewable Energy Magnetics: Built for the Components Inside Your System

Inverter-fed renewable systems put magnetics through conditions standard catalog parts weren’t built for: high-frequency switching content riding on the fundamental, bidirectional operation at the BESS interface, and load cycling that follows weather and dispatch. Components that look adequate on a datasheet quietly run hot, drift out of tolerance, and shorten the duty cycle of everything around them — usually over months, not in a single event.
Custom Coils USA designs and builds the small-format magnetics that go inside renewable energy systems: gate drive and sense transformers, control-power and isolation transformers, toroidals, filter inductors, and EMI chokes. We’re a VPI dry-type specialty shop with transformers up to roughly 2 kVA. We don’t build the substation-class iron or the main inverter step-up transformer — those aren’t in our market. We build the components that go inside the inverter, the BMS, the monitoring rack, and the balance-of-plant control hardware. OEMs and integrators in solar, wind, and battery storage have been working with us for decades because the components hold up across the full duty cycle.

Products We Build for Renewable Energy Projects

Inverter-Internal Transformers (Gate Drive, Sense, Control Power)

Inside every inverter is a layer of small transformers that don’t appear on the system one-line but determine whether the converter starts, switches cleanly, and keeps reporting back to its controller. Gate drive transformers couple control signals into IGBT and SiC switch stages with the propagation delay and isolation rating your driver demands. Current and voltage sense transformers feed measurement and protection electronics. Control-power transformers run the housekeeping rails. We build all three to your topology, frequency, and isolation specification.
 

Filter Inductors & EMI Chokes

Common-mode chokes on AC and DC lines, differential-mode filter inductors, and DC-link chokes — sized to the current ratings, switching frequencies, and EMI targets of your converter. Available with silicon steel, ferrite, amorphous, and nanocrystalline cores depending on frequency and loss budget. Each design is built to your specification rather than pulled from a generic catalog, with attention to saturation behavior, thermal performance, and acoustic noise under continuous duty.

Toroidal Transformers for Control & Monitoring Hardware

Toroidal transformers are the right answer where you need low stray flux, low audible noise, and high efficiency in a small package — auxiliary supplies, instrumentation, isolated control rails, and monitoring equipment that lives near high-power gear on a renewable site. Efficiencies in the 95–99% range, dramatically reduced stray field compared with EI-core equivalents, in custom turns ratios and winding configurations up to our 2 kVA build envelope.

Isolation Transformers for Control & Protection Circuits

Isolation transformers put a hard galvanic barrier between the generation system and the control electronics that monitor and protect it. The product is conceptually simple; engineering matches the design to the actual fault conditions, leakage capacitance limits, and creepage/clearance requirements your application has to meet. Built VPI dry type for long-term reliability in real operating environments.

Why OEMs and System Integrators Work with Us

• Designs are built to your converter topology and application requirements — not pulled from a generic catalog
• Wound, vacuum-pressure-impregnated, assembled, and tested in-house in the USA — no overseas hand-offs, 4–8-week lead times
• Compliance documentation as required: UL, IEC, IEEE, CE — witnessed FAT available on request
• You’re talking to engineers, not account managers — the person quoting the job understands what you’re asking for

Frequently Asked Questions

Q1: What kind of magnetics does Custom Coils build for renewable energy systems?

Small-format magnetics that go inside inverters, BESS systems, and balance-of-plant equipment — gate drive and sense transformers, control-power and isolation transformers, toroid’s, filter inductors, and EMI chokes. We’re a VPI dry-type specialty shop with transformers up to about 2 kVA. We don’t build the utility-class substation iron or the main inverter step-up transformer; we build the components inside the converter and the control/monitoring hardware around it.

Q2: How are renewable energy magnetics different from standard ones?


Standard utility magnetics are designed around 50/60 Hz steady state. Renewable systems run inverters that put significant harmonic content on top of the fundamental, cycle hard with weather and dispatch, and frequently push power both directions through the same component. Conductor sizing, insulation systems, and core-loss budgets all must account for that — even on the small-format magnetics inside the converter.

Q3: What do filter inductors and EMI chokes do in a solar or wind system?

Two main jobs. Common-mode and differential-mode filter inductors clean up switching harmonics and reduce conducted EMI on AC and DC lines. DC-link chokes inside the converter smooth current ripple and de-couple the switching stage from the DC source — PV string, BESS pack, or rectified wind generator output.

Q4: Why use toroidal transformers on a renewable site?


For auxiliary and control applications; not the main power path. Toroid’s run efficiently with low stray field and low audible noise, which matters where SCADA, monitoring, and protection electronics share a cabinet or enclosure with generation-side equipment.

Q5: What are your lead times for custom renewable energy magnetics?


4–8 weeks from finalized specification to delivery. Engaging us early in your design cycle is the best way to keep the magnetics off the critical path.